Xiao-Ai-Ping Injection Enhances Effect of Paclitaxel to Suppress Breast Cancer Proliferation and Metastasis via Activating Transcription Factor 3

Chemotherapy is an effective treatment for invasive breast cancer. Paradoxically, many recently published findings showed that the first-line chemotherapeutic agent paclitaxel (PTX) showed pro-metastatic effects in the progress of treating breast cancer. Xiao-Ai-Ping (XAP) injection, composed of a traditional herbal medicine, Marsdenia tenacissimae extract, is known to exert antitumor effects on various cancers. However, there are few experimental studies on breast cancer. The underlying mechanism of the antitumor effect of XAP combined with chemotherapy agents has not been fully understood. In the present study, we sought to find the antitumor effects of XAP combined with PTX in vitro and in vivo. The data demonstrated that the combination of XAP with PTX resulted in remarkable enhancement of the pro-apoptotic, migration-inhibiting, and anti-invasive effects of PTX in vitro. Significantly, further study showed the overexpression of ATF3 in PTX-treated cell, while XAP counteracted the change of ATF3 induced by PTX. Moreover, it showed that combination treatment could promote the inhibition of tumor growth in MDA-MB-231 cell xenograft mouse model. Compared with PTX treatment, the downregulation of ATF3 indicated that ATF3 played a pivotal role in the combination of XAP with PTX to exert a synergistic effect. Overall, it is expected that PTX combined with XAP may serve as an effective agent for antitumor treatment, and dampening ATF3 maybe a potential strategy to improve the efficacy of PTX.